I'm updating to 1.16 from 1.12. I see their is a new mod api kicking around. So what is the general consensus on this argument? Are moders stepping away from forge for fabric? I'd run both if I could (can I?)
Depends on what your looking for. I've been with the Fabric Devs (over time, never talked to them prior to Fabric, just knew of their mods) for a while as a reviewer/player/bug reporter since 18w50a when it was becoming a thing and just helped out while reviewing mods, making modpacks, making wikis and forums for either modloader over time.
A few of what you'd expect on 1.12.2 have moved to 1.15.2 or 1.16 versions on Forge. Many big tech mods, Ice & Fire Dragons, Biomes O' Plenty and more but obviously there is a lot of good new or similar enough alternatives to cover categories you may be after. Depends on what your looking for.
Fabric was created due to differences between Mod Devs and the Forge Team. Removal of features, taking to long to update to 1.13 and bad communication made many create Rift (a 1.13/1.13.2 modloader that was dropped for particular reasons I won't get into) and then Fabric. In the Fabric Discord you see the odd finger pointing or the Forge Team letting split in Episode 1 of the 1.15 ForgeCraft season but yeah otherwise usually you can just use mods for either modloader and not notice a thing if you ignore comment sections and go for the mods. I know this from just being an outsider/being with Fabric since it was public as a player and the Mod Devs know me as a major reviewer of many of their mods/my forum threads and I just keep what I see/know as background knowledge as I enjoy mods like any other Minecraft Mod Player. Reporting bugs, discovering mods, helping out in cases like this, etc. There isn't much toxicity but it is noticeable among players/mod devs but many people use whatever they want and are fine with using Forge still, Fabric only or both.
Fabric is good for lightweight performance for players, while Forge requires a bit more to use, it's not that much more but it can be noticeable.
Fabric is updated to snapshots, and releases as fast as those are released by Mojang. Forge takes time which is fair due to how it's developed/it being probably like a recreation of the game I'd assume but yeah there is that difference.
Mod wise it depends some have moved from Forge to Fabric, some are on both and many are still for Forge. There is many ports of mainstream tech mods like Applied Energistics 2, ones that have moved to it like Tech Reborn and similar mods (like Roughly Enough Items as a Just Enough Items mod that is more finished then JEI is currently at least having used 1.14 to 1.16.3 alpha versions and it feeling very stable but not feature rich) to popular ones like Kibe being like Open Blocks but when it comes to ports of noticeable ones or unique ones/small ones most people think Fabric is good for small Vanilla+ like mods similar to Liteloader in a way which it is but does have many not worth content mods you just have to look for the different types in whatever categories your into of tech, adventure, tools, utility, HUD, world gen, mobs and more. There is a good mix of biome mods that are Biomes O' Plenty close like Terrestria or Traverse being ported, Age of Exile as an RPG/Diablo style mod or a few tool ones that are pretty standard or Materialization for a Tinkers like one and others that fill in other gaps. An Optifine "contender apparently" being Sodium that Optifine fans meme (at least for the videos I've seen they can't even try to make it believeable). It's a fine performance mod basically or there is dynamic light, connected textures and more mods on either modloader if you prefer.
Fabric and Forge mods aren't compatible like Forge and Liteloader are on 1.12.2 and before which can bother some but I don't notice it as I consider any mods regardless of using two different modloaders, but due to being a Reviewer/Modpack maker that's just something I've gotten used to over time and most fans aren't that way.
There is a lot out there as someone that's made many modpacks for both modloaders and not focusing on the 'mainstream hits' like those that do for fighting over the best platform (of the few I've seen, but I think most people just use which they prefer).
The Forge community from my experience on the Fabric API Curseforge page's commment section are a pain (not everyone is bad though, some use both, some stick with Forge and do there own thing of course, some use only Fabric now), they don't appear often but you know they just want to complain. Any community can get toxic but you don't see it often, though I don't go to Reddit I just go to the Curseforge pages I want to and the MCForums/Fabric Discord to get a bit of what's going on from the community and Mod Dev's thoughts. Otherwise I just do my own thing for the community for mod discovery/assistancing in cases like this rather than caring about all the 'which platform is better' nonsense. But just so you know.
While I don't like to plug my stuff usually. If you want to see what's on offer for both I can direct you to my Youtube channel (https://www.youtube.com/channel/UCyiHWb7p9yxDH1vaYZPdo9w/playlists) so you can see what's out there as I cover almost everything Fabric has while others pick and chose those they find interesting. And make videos covering mods from both daily across 1.14 to 1.16.3 compared to most that just do a common/updated version.
I also have forums (two of in my signature but otherwise you will see often in the Mod Discussion section of the MCForums being updated) that I update showing mods for both modloaders that release every 1-3 days if your curious and to help users of the forum discover/tell the difference between what is for Forge & Fabric as it can be tricky sometimes.
I have a 1.14, 1.15 & 1.16 one that I maintain often with a few others like Legacy Fabric for 1.8.9 and older versions and other odd things but they are part of the 1.14+ Fabric/Forge stuff people usually talk about/point to but are still noteworthy for knowing what's out there for Fabric.
Hopefully my and TileEntity's comments were helpful. I can go a bit over board but I hope it was beneficial.